1. Field of the Invention
This invention relates to an electrographic apparatus which can obtain copies of a thick manuscript and a sheet manuscript.
2. Description of the Prior Art
Various kinds of electrographic apparatuses have heretofore been proposed and used in practice. One of these conventional electrographic apparatuses is mainly used for obtaining copies of a thick manuscript such as books or the like, while the other electrographic apparatus is mainly used for obtaining copies of a sheet manuscript.
In the electrographic apparatus mainly used for obtaining copies of the thick manuscript, in the case of obtaining copies of the sheet manuscript, the sheet manuscript is disposed on a manuscript carriage and urged against it by a manuscript holding cover. The manuscript carriage or a projection optical system is reciprocated for number of times corresponding to the number of sheets to be copied, thereby obtaining copies. In this case, the operation of opening and closing the manuscript holding cover in order to set the sheet manuscript on the manuscript carriage is troublesome in operation. In addition, wind pressure produced when the manuscript holding cover is opened and closed tends to displace or blow off the sheet manuscript set beforehand, thereby rendering the operation very inconvenient and bad in efficiency. In general, the kind of the manuscript to be copied belonging to the sheet manuscript is far larger than that belonging to the thick manuscript. As a result, the above is the important drawback inherent to the electrographic apparatus mainly obtaining copies of the thick manuscript.
On the other hand, the electrographic apparatus mainly used for obtaining copies of the sheet manuscript is classified into one type in which the sheet manuscript is directly inserted into and passes through a light exposure portion so as to be scanned by exposed light and into another type in which if the sheet manuscript is introduced into the apparatus it is automatically set to a given position where it is repeatedly scanned by the exposed light for the number of times corresponding to the number of the sheet manuscripts to be copied and then is automatically discharged from the apparatus.
The former type electrographic apparatus can insert the sheet manuscripts in succession into the light exposure portion and hence is very rapid in operation if compared with the above mentioned electrographic apparatus mainly used for obtaining copies of the thick manuscript and adapted to change a previous manuscript to the next manuscript after the previous manuscript has been scanned by the exposed light.
In addition, the former type electrographic apparatus is not required to use a reciprocating mechanism for the manuscript carriage or projection optical system, so that the apparatus as a whole is simple in construction and can be manufactured in a less expensive manner. But, in the case of obtaining a plurality of copies from the same manuscript, the manuscript must repeatedly be inserted into the light exposure portion for number of times corresponding to the number of copies to be obtained, and as a result, the apparatus becomes very troublesome in operation and bad in efficiency.
The latter type electrographic apparatus has the advantage that a desired number of copies can be obtained by inserting the sheet manuscript only one time into the apparatus. But, this apparatus has the drawback that the apparatus as a whole is complex in construction, that a manuscript feed path is complex in construction and hence is troublesome in feed operation and that the manuscript tends to be easily broken.
The former type electrographic apparatus can obtain copies of the thick manuscript with the aid of a suitable auxiliary means. On the contrary, it is almost impossible to obtain copies of the thick manuscript by the latter type electrographic apparatus. To the electrographic apparatus mainly used for obtaining copies of the thick manuscript has been added a sheet manuscript feed mechanism which can automatically feed a sheet manuscript disposed on a manuscript carriage and automatically discharge it after a required number of sheets have been repeatedly scanned by the exposed light. But, such kind of sheet manuscript feed mechanism is complex in construction and large in size and hence is generally used only for an expensive high speed copying machine.
The auxiliary means added to the former type electrographic apparatus mainly used for obtaining the sheet manuscript and operative to obtain copies of the thick manuscript comprises a sheet manuscript driving roller, its corresponding driven roller and an end driven roller independent of the driven roller and arranged at the outside of the driven roller, the end driven roller being co-operative with the driving roller so as to feed a light transmission thin plate for the thick manuscript and constructed such that in the case of obtaining copies of the thick manuscript the sheet manuscript feed driven roller is pushed aside or removed and the light transmission thin plate with the thick manuscript disposed thereon is held between the driving roller and the end driven roller so as to be fed and scanned by the exposed light. That is, the light transmission thin plate in such auxiliary means is fed at a given feed speed by means of a friction force produced between the driving roller and the end driven roller. But, in the case of obtaining copies of the thick manuscript by means of such auxiliary means, an operator is always required to hold down the thick manuscript by a pressure which is sufficient to prevent the thick manuscript from displacing or from rising during feed of the light transmission thin plate. As a result, unreasonable force is subjected to the light transmission thin plate while it is fed. The frictional force produced between the driving roller and the end driven roller for feeding the light transmission thin plate sandwiched therebetween becomes changed. As a result, it is impossible to maintain the given feed speed, thereby inducing a blur in copy or an inclined displacement of the light transmission thin plate. As a result, in the case of using such auxiliary means, the operator is required to have a certain order of skill and operate with the greatest possible care. In addition, the end driven roller is projected from the surface along which the light transmission thin plate passes, so that the operator is also required to pay attention not to damage his finger or the manuscript got caught in the projected end driven roller.
In the case of obtaining a plurality of copies from the same manuscript, the above mentioned operation must be repeated, so that the operation becomes more complex and the rate of damaging the precious manuscript becomes high. In addition, the separate need of the driven roller exclusively used for feeding the thick manuscript makes the apparatus complex in construction.
The applicant has been proposed an electrographic apparatus which can eliminate the above mentioned drawbacks, that is, which can obtain copies of sheet manuscript and thick manuscript without damaging the manuscript in a simple manner, and which can obtain a desired number of copies with an extremely high efficiency by scanning the manuscript only one time by exposed light (U.S. Patent Application Ser. No. 26,760 and German Patent Application No. P29 15633.0).
The proposed electrographic apparatus comprises a substantially rectilinear manuscript feed path including a slit light exposure portion through which is projected a manuscript image; a manuscript feed mechanism including upper and lower feed mechanisms arranged above and below said manuscript feed path at said slit light exposure portion with said manuscript feed path interposed therebetween, said upper feed mechanism being mounted movably with respect to said slit light exposure portion; and a photosensitive body for memorizing said manuscript image projected through said slit light exposure portion thereon as an electrostatic latent image; the apparatus being constructed and arranged such that in the case of obtaining copies of a sheet manuscript said sheet manuscript is fed by said manuscript feed mechanism under a condition that said upper feed mechanism is mounted on said lower feed mechanism and scanned by exposed light by one time and in the case of obtaining copies of a thick manuscript a thick manuscript carriage on which is disposed said thick manuscript is fed by said lower feed mechanism under a condition that said upper feed mechanism is moved from said lower feed mechanism and scanned by exposed light by one time, thereby producing on said photosensitive body an electrostatic latent image corresponding to said manuscript image and obtaining a plurality of copies on the basis of said electrostatic latent image.
In this electrographic apparatus, use is made of a thick manuscript carriage comprising a flat transparent light exposure portion on which a thick manuscript to be copied is disposed, a carrying member which is driven without skipping by a thick manuscript feed mechanism of the electrographic apparatus and a member for determining a position of the thick manuscript at the light exposure portion; the light exposure portion, the carrying member and the position determining member being assembled into a single unit to form the thick manuscript carriage. The thick manuscript carriage is mounted on the thick manuscript feed mechanism with its one side parallel to the feed direction set along an edge guide provided on the electrographic apparatus. Then, a thick manuscript can be fed under a condition that the thick manuscript is positioned correctly.
In such an electrographic apparatus, it is preferable to arrange an edge guide for determining a position of a side of the thick manuscript carriage outside an edge guide for determining a position of a side of a sheet manuscript. However, in such an apparatus the two edge guides must be changed over each other when a manuscript to be copied is changed from a thick manuscript to a sheet manuscript or vice versa. For this purpose, in said apparatus the edge guide for a sheet manuscript can be displaced with respect to the edge guide for the thick manuscript feed carriage, the latter edge guide being fixed. However, this change of edge guides is manually operated by a user and is often forgotten by the user. In this case, a position of a manuscript to be copied is not correctly set so that the manuscript cannot be recorded on a recording paper. In addition, this manual change requires a complicated and troublesome operation for a user of the electrographic apparatus.